1. Field of the Invention
The present invention relates to a mixing device for admixing gas or vapor and liquid in a vessel where a vapor phase and a liquid phase are flowing concurrently. The purpose of the device is to equilibrate the temperature and chemical composition of the outlet mixture exiting the device. The invention is suited for but not limited to the application of admixing hot hydrogen rich treatgas and hot hydrocarbon liquid with a cold quench stream between two adjacent beds of catalyst in a hydroprocessing reactor like a hydrotreating or hydrocracking reactor. The invention furthermore relates to a catalytic reactor comprising a mixing device mentioned above, a method of admixing vapor and liquid in a concurrent flow thereof and a product produced by said method.
2. Related Art
A large number of mixing devices for two-phase concurrent vessels have been described in literature and patents. The majority of these devices belong to one of the six types given below:
Type 1: Vortex Mixers with Inlet Chutes Provided in a Collection Tray
An example of such a design is given in U.S. Pat. No. 3,541,000. The mixer consists of a horizontal collection tray plate 6. The collection tray plate is provided with a plurality of sloped chutes 32/34. The entire process stream of vapor and liquid from the catalyst bed above passes through these inlet chutes at high velocity. Below the collection tray is an annular mixing box 8. The exit jets from the chutes have horizontal components and result in a swirling fluid motion inside the annular mixing box. The fluids are then passing over an internal weir 12 and then vertically downward through a center opening 10. At the outlet of the opening 10 the cold quench fluid is added through perforated distributor pipes in a spider arrangement 30. Below the mixer a distribution tray 14 is located for rough distribution of the liquid. Tray 14 also serves as an impingement plate for the high velocity fluids exiting the opening 10. Below the rough distribution tray a distribution tray 4 is located for final distribution of the liquid.
Other examples of vortex mixers are the following: In U.S. Pat. No. 4,836,989, a mixer similar to the mixer in U.S. Pat. No. 3,541,000 is described. However for improved mixing of the quench fluid, with vapor and liquid from the catalyst bed above, the quench fluid is added through perforated pipe distributors 13 upstream from the collection tray 12 instead of downstream from it. In U.S. Pat. Nos. 5,837,208 and 5,989,502 and in WO 02/48286, mixers similar to the mixer in U.S. Pat. No. 4,836,989 are described.
Type 2: Swirl Box Mixers with Radial/Horizontal Inlet Flow
An example of such a design is given in U.S. Pat. No. 3,353,924. The mixer consists of a collection plate 6. The cold quench media is added through a perforated pipe ring 11 above the collection plate. The vapor and liquid from the catalyst bed 3 above the mixer and the quench fluid enter the swirl box 7 through a plurality of inlet ports 8. Unlike the vortex mixer designs mentioned above, the flow through the inlet ports to the swirl box mixer is mainly in the horizontal/radial direction. The inlet ports are provided with vanes 9 which introduce a swirling motion to the fluids inside the swirl box 7. The fluid exits the swirl box through a center opening 13a. Below the center opening a perforated impingement plate 14 is provided with vertical baffles 16.
Other examples of swirl box mixers are the following: In U.S. Pat. No. 3,787,189 a swirl box mixer similar to the mixer in U.S. Pat. No. 3,353,924 is described. However the inlet openings and vanes of the swirl box have different designs, and the impingement plate 23 below the center opening 20 is not perforated. Vanes 22 introducing a swirling motion to the fluids exiting the mixer below the collection plate 18 have replaced the radial arranged vertical baffles at the mixer outlet. In U.S. Pat. No. 5,462,719 a swirl box mixer similar to the mixer in U.S. Pat. No. 3,353,924 is described. The vapor and liquid are first passed through radial perforations in a cylindrical baffle 24 then through vanes 22, which result in swirling fluid motions inside the swirl box. The fluids exit the swirl box through the central opening 21 and enter a second mixing box located below the collection plate 20. In the second mixing box the fluids flow outward in a radial direction and exit the mixer through the radial perforations in cylindrical wall 26.
Type 3: Bubble Cap Like Mixers
An example of such a design is given in U.S. Pat. No. 5,152,967. The mixer consist of a collection plate 16 and a cap 18, 19 overlaying a downcomer 17. The cap and downcomer define the first mixing swirl chamber. The sidewalls of the cap 19 are provided with angled openings. As the vapor and liquid enter the first swirl chamber through the angled openings, a swirling motion is introduced. The fluids flow first upward and over the upper edge of downcomer 17 and then downward through the downcomer and a central opening in the plate 16. The present mixer is also provided with a second swirl chamber located below the first swirl chamber with inward radial flow.
Other examples of bubble cap like mixers are the following: In U.S. Pat. No. 6,183,702 another bubble cap like mixer is described. The mixer consists of a collection plate 1125, which holds a certain liquid level. The collection plate is provided with vertical baffles 1130 which promote a swirling motion of the liquid on the plate 1125. The swirling motion is further intensified by quench fluid jets exiting from pipes 1140. On the collection tray a bubble cap like mixer consisting of a slotted cylindrical cap 1150 overlaying a cylindrical downcomer 1165 is mounted over a central opening in plate 1125. The annular space between the cap and the downcomer is provided with semi-spiral shaped baffles 1155. The vapor enters the annular space through the slots in the cylindrical wall of cap 1150, whereby the vapor “lifts” the liquid up into the annular space, and the vapor and liquid flow upward through the annular space. A swirling motion is introduced in the annular space by baffles 1155. The vapor and liquid flow down through the downcomer and through the opening in the collection plate 1125. U.S. Pat. Nos. 3,824,080, 3,824,081 and 5,403,560 are other examples of bubble cap like mixers.
Type 4: Mixers with Separate Mixing of Vapor and Liquid
An example of such a design is given in European patent no. 716,881. The mixer consist of a collection plate 20 with a center opening 30. Above the center opening a vapor swirl box 100/55 for mixing the vapors is located. The vapor swirl box is provided with apertures 95 and swirling means 105. The collection plate 20 is provided with other openings 40 for liquid flow. The openings are connected with channels 65 to direct the liquid toward the centerline of the reactor. During normal operation the collection plate 20 holds a certain liquid level, and the vapor enters the vapor swirl box mixer 100/55 and exits through the center opening 30 while the liquid is bypassing the swirl box mixer through the parallel liquid passages 40/65. Below the mixer a rough distributor/impingement plate 90 is located.
Another example of a mixer with separate mixing of vapor and liquid is given in U.S. Pat. No. 5,935,413.
Type 5: Baffled Box Mixer with Vertical Flow
An example of such a design is given in U.S. Pat. No. 4,233,269. The mixer consists of an inlet feed conduit 12 where the vapor and liquid enter the mixer. From the inlet feed conduit, the fluids are passed through two circular mixing orifices formed by doughnut plates 32 and 36 and through one annular flow restriction formed by the disc 34.
Type 6: Baffled Box Mixer with Horizontal Flow
An example of such a design is given in U.S. Pat. No. 5,690,896. The mixer is built as an integral part of the catalyst support system. Vapor and liquid are collected in the annular collecting trough 24. Quench fluid is added to the annular collection trough through quench pipes 22 and 23. The vapor and liquid flow through the annular collection trough to the mixer box 30 located between the support beams 14 and 15. The entire process stream enters the mixer box at the inlet 36. The mixer box consists of a single flow channel with a 360° turn in flow direction. After the 360° turn in the mixer box the fluid exits through the center opening 37.
U.S. Pat. No. 3,705,016 describes a mixer consisting of a screen 11/12 located on a collection and catalyst support plate 8. The screen is covered by inert support material 7. Quench fluid is injected in the catalyst bed above the plate 8. The vapor and liquid can pass through the screen 11/12 while the inert material cannot. After having passed through the screen, the vapor and liquid flow vertically through the center opening in the plate 8. Below the plate 8, a horizontal mixing box, comprising a horizontal bottom plate 16 and vertical baffles 20, 21, 22 and 23, is located. The fluids exiting the center opening are first divided into two horizontal streams. Then each of the two streams is again divided into two streams resulting in a total of four streams. At the mixer exit two of these four streams are recombined and sent to one side of the reactor cross section while the remaining two streams are also recombined and sent to the other side of the reactor cross section. Finally the vapor and liquid are distributed through a perforated tray 25.
Another example of a baffled box mixer with horizontal flow is given in U.S. Pat. No. 3,977,834. A mixer consisting of a plurality of parallel mixing boxes 13 is described. The mixing boxes are located between the catalyst support beams 7 and a quench fluid is added between the beams upstream from the mixer boxes through pipes 11.